You get this view when CSS aren't loading (i.e. are blocked).

If you use extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) that can block (wanted) content (e.g. Adblock Plus, NoScript, Ghostery, uBlock Origin) always make sure such extensions do not block (wanted) content.

• make sure your extensions and filters are updated to the latest version

You can check the Web Console (Tools -> Web Developer) for messages about blocked content and about the presence of mixed or unsafe content.

• https://developer.mozilla.org/en/Tools/Web_Console

You can check the Network Monitor to see if content is blocked or otherwise fails to load.

• https://developer.mozilla.org/en/Tools/Network_Monitor

Use "Ctrl+F5" or "Ctrl+Shift+R" to reload the page and bypass the cache to generate a fresh log.

Getting mixed content blocking. https://developer.mozilla.org/en-US/docs/Web/Security/Mixed_content/How_to_fix_website_with_mixed_content- Say's "For other domains, use the site's HTTPS version if available. If HTTPS is not available, you can try contacting the domain and asking them if they can make the content available via HTTPS."

The site is HTTPS

Note that it is possible that you need to use the HTTP protocol and not the HTTPS protocol to access this website if there is that much mixed content in case you have forced a security connection.